2014 June 12 | Jing Fan, Jiangbin Ye, Jurre J. Kamphorst, Tomer Shlomi, Craig B. Thompson, and Joshua D. Rabinowitz
This study investigates the production of NADPH in proliferating cells, focusing on the oxidative pentose phosphate pathway (oxPPP) and serine-driven one-carbon metabolism. The authors developed a deuterium tracer approach to directly measure NADPH redox-active hydrogen labeling, allowing them to quantify the fractional contribution of the oxPPP to total cytosolic NADPH production. They found that the oxPPP accounts for 30-50% of NADPH production, with a total rate of ~10 nmol uL-1h-1. Additionally, they confirmed that serine-driven folate metabolism contributes to NADPH production, with the main pathway involving the oxidation of 10-formyl-tetrahydrofolate to formyl-THF, which is then reduced to NADPH. Knockdown of methylenetetrahydrofolate dehydrogenase (MTHFD) genes resulted in decreased cellular NADPH/NADP+ and GSH/GSSG ratios, indicating the functional significance of folate metabolism in NADPH production. The study also highlights the importance of NADPH in antioxidant defense, as MTHFD knockdown decreased the ratio of reduced to oxidized glutathione and impaired resistance to oxidative stress. Overall, the research provides a comprehensive understanding of NADPH production and its role in cellular metabolism.This study investigates the production of NADPH in proliferating cells, focusing on the oxidative pentose phosphate pathway (oxPPP) and serine-driven one-carbon metabolism. The authors developed a deuterium tracer approach to directly measure NADPH redox-active hydrogen labeling, allowing them to quantify the fractional contribution of the oxPPP to total cytosolic NADPH production. They found that the oxPPP accounts for 30-50% of NADPH production, with a total rate of ~10 nmol uL-1h-1. Additionally, they confirmed that serine-driven folate metabolism contributes to NADPH production, with the main pathway involving the oxidation of 10-formyl-tetrahydrofolate to formyl-THF, which is then reduced to NADPH. Knockdown of methylenetetrahydrofolate dehydrogenase (MTHFD) genes resulted in decreased cellular NADPH/NADP+ and GSH/GSSG ratios, indicating the functional significance of folate metabolism in NADPH production. The study also highlights the importance of NADPH in antioxidant defense, as MTHFD knockdown decreased the ratio of reduced to oxidized glutathione and impaired resistance to oxidative stress. Overall, the research provides a comprehensive understanding of NADPH production and its role in cellular metabolism.